The rotor of a fractional horsepower or miniature motor is normally mounted for rotation in bearings supported by an integral end wall of a drawn metal can forming the motor casing and by an end cover or cap closing the casing. The end wall has a hole through which the motor shaft extends. The wall may be deformed to form a recess or housing for the shaft bearing as shown, for example, in GB 2207291. This process is complicated and thus costly to perform with a high degree of accuracy.
As an alternative, the bearing may be retained in a bearing retainer which is fitted to the hole in the end wall of the motor casing. The retainer may be a plastic part as shown, for example, in GB 1216146. Here, a plastic ring is used to grip the bearing and retain it with respect to the casing. However, as indicated, the plastic material which makes that method economically viable is not suitable for sleeve or self-aligning sleeve bearings with the motor casing providing the lateral support directly to the bearing.
Machined bearing retainers, usually turned parts, formed from aluminium have proved very satisfactory in retaining the bearing axially but there is a problem with the retainer rotating with respect to the casing as the retainer by necessity is round and fitted to a round hole. Also, the cost of providing machined parts is becoming a significant cost component in a miniature motor.
Hence, there is a need for an alternative to plastic and machined bearing retainers for the end wall of motor casings for miniature motors.